The invention relates to security locks with pistons and cylindrical key.
The use of cylindrical keys, in particular in the field of the automobile, offers great advantages, in particular by reason of the possibility of introducing the key in any angular position, the coupling between the key and the lock cylinder taking place in an angular position determined by the co-operation of a male profile of the key with a corresponding female profile of the cylinder.
These known locks, if they give full satisfaction, are however quite costly in manufacture by reason of the fact that, to prevent the pistons of the cylinder from dropping into the key passage in the absence of the key, these pistons of the cylinder must be equipped with a shouldered head and stop shoulders for these pistons must be formed in the radial bores of the rotor which receive these pistons. Moreover the presence of a shoulder in the radial bores of the rotor has the effect that the pistons are guided only over a short length corresponding to the smallest diameter of the bore. Poor guidance and a risk of binding of the pistons can follow.